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Posted: March 26, 2010

Thanks for the quantum memories: Research may lead to faster, more secure computers

(Nanowerk News) Virginia Lorenz, who recently joined the University of Delaware faculty as an assistant professor of physics and astronomy, is working on one of the hottest areas in physics -- quantum memories. These devices store information in a flash of light and may serve as the basis of future communications networks.

Lorenz recently co-authored the Nature Photonics article ("Towards high-speed optical quantum memories") with colleagues at the University of Oxford, where she did her postdoctoral research with Prof. Ian Walmsley. She tells UDaily about this fascinating field.

Q. What exactly are quantum memories?

A. Like our own human memory, a quantum memory is a device in which we can store and retrieve information. A quantum memory stores bits of information like a computer. However, unlike everyday computer memory, which uses 1's and 0's to represent information, in a quantum memory the bits can be 1 and 0 at the same time. This is what makes a quantum memory quantum. Quantum refers to the fundamental nature of particles such as atoms and photons. Although in everyday life, things like a light switch are either on or off, when you zoom in to the level of atoms, particles can be in more than one state at a time. A quantum memory is a device that can store the properties of a quantum particle without causing it to be in one state or another.

Q. What advantages would quantum memories provide to computing?

A. The information stored by a quantum memory is called a quantum bit, or qubit. Qubits can be used to perform some mathematical algorithms much faster than current computers, such as factoring the very large numbers used as security keys in secure communication networks. Hence, there is current interest in building quantum computers that use qubits rather than the 1's and 0's of today's computers. Quantum states can also be used to transmit information in a way that prohibits undetected eavesdropping. Quantum memories are important in achieving such secure communication in a somewhat similar way as cell phone repeater stations are important in transmitting signals across long distances.

Q. What did you and your colleagues at Oxford achieve?

A. My colleagues and I built a prototype quantum memory. The information was encoded in an extremely fast flash, or pulse, of laser light, only 300 trillionths of a second long, and the storage medium was a large number of atoms in the gas phase. Although with respect to the fastest laser pulses available ours was relatively slow, it was the fastest pulse to be stored and retrieved in a memory to date, potentially increasing the current data rate more than 100-fold.

Q. What is the next step in the research?

A. For the quantum memory project, which continues on at the University of Oxford, the next step is to store and retrieve a quantum particle of light, called a photon, which would demonstrate that the memory is capable of storing quantum information useful for quantum computation and communication.

In my research group here at UD, we are using quantum states of light to improve our ability to probe the states of atoms and molecules. It turns out that quantum states of light can provide information about matter that regular, or classical, light cannot. In particular, quantum states of light can enhance signals from light-matter interactions that would otherwise be hidden if using classical light. Our work could have implications for experiments that suffer due to unwanted signals and, albeit distant, provide insight into the efficient conversion of energy.